Sounding condenser



Filed Feb. 26, 1929 II I P tented Aug. 4, 1931 PATENT OFFICE HANS VOGT, OF BERLIN, GERMANY SOUNDING CONDENSER Application filed February 26, 1929, Serial No. 342,705, and in Germany May 16, 1928.

My invention relates to sounding condensers. In my copending application,

'Serial No. 306,158, dated September 15,

1928, therehas been described and claimed 5 a sounding condenser whereof the diaphragm consists of a thin foil of a light metal or alloy of high elasticity and strength, the said metallic foil being kept under high tension in radial direction and I mounted between two stationary perforated capacityvsurfaces or condenser armatures so as to be free to oscillate within the gap between the two spaced capacity surfaces.

'The object of the present invention is to 5 provide a sounding condenser of the indicated type which in some respects may be regarded simply as an improvement over the structure describedin said previous application, and wherein the acoustic frequency' range of the oscillatory or vibratile diaphragm is increased for the purpose of reproducing both the sounds of highest pitch and the sounds of lowest pitch, in

their natured timbre and with greater loudness and sonorousness than hitherto could be attained "by loud-speaking appliances.

As a fact the efficiency of a sounding condenser depends upon-the properties of the electrostatic field acting to excite the vibratile diaphragm, that is to say, the condenser is the more eflicient the more uniform and stronger the electrostatic field is, and as the latter increases in accordance with the square of the approachdf the capacity sur faces or condenser armatures, the said surfaces obviously ought to be approached or spaced as close as possible without inter- I j fering witlr thef greatest oscillatingdeflectio'n'o'r amplitude of the diaphragm. Evi- 40 dently the oscillating range or amplitude of the diaphragm is greatest at the centre thereof and gradually decreases towards the periphery thereof since the peripheral edge of the diaphragm is fixed and immovable.

Consequently in case of flat capacity sur faces arranged-in parallelism so as to be equally spaced at the centre and at any other or peripheral points, the intensity or strength of the electrostatic field-will gradually decrease towards the periphery of the two surfaces due to the width of the gap required between the latter in order to allow of the central portion of the diaphragm to freely oscillate between the said two surfaces. 7

According to the present invention the stationary or interconnected rigid capacity surfaces of the condenser are so shaped thatwhen they are duly assembled, the gap or space therebetween is greatest in the vicinity of the alined axes thereof or centrally and lating diaphragm will extend oramount to 7 a fraction of a millimetre only, even at the centre or the point thereof where the amplitude is a maximum, it is obvious that the sphericity of the opposite surfaces of two capacity bodies will be extremely slight only.

Another object of my invention is to provide means, such as screws, in the one capacity. body or in both, and which are adapted, to force the centres of the fixed capacity bodies apart from each other so as to impart tothe latter the required slight spherical or concave form. In this way it is possible to' ascertain experimentally the best suitable degree of sphericity or concavity in each individual condenser by adju'sting the set screw or screws so as to ensure the best effect as regards sound and timbre. 7

With the above and other objects in View, reference is bad to the followlng specification ,and'dr'awings in which there are ex hibited several examples or embodiments of the invention which are in no way intended as. a-limitationupon the scope of the subjoined claims, as it is' to be clearl understood that variations and mod1fications which fairly fall within the true scope of said claims may be resorted to when found expedient.

' ing condenser constructed in accordance.-

In the accompantying drawings forming a part of this speci cation and showing for ex'emplification preferred forms and manners in whichythe invention may be embodied and practised, but without limiting the claimed invention to such illustrative instances:

Figure 1 shows in front elevation a soundwith the present invention; vFi' re 2 is a View in vertical cross-section o the same;

and Figures 3 and 4- are similar sectional views of modified forms of the condenser.

Referring to Figures 1 and 2, a and a in: j dicate the two stationary fixed capacity surfaces or'condenser'arma'tures and]; denotes the vibratile diaphragm with its circular peripheral edge clamped between two clamping rings a so as to be stretched at high radial tension, the arrangement of the assembled parts being such that the diaphragm b occupies a position in the median lane of the free s ace or gap between, the nner or opposite aces of the. two capacity bodies a and a; In the centre of the capacity surface or body a a threaded bore is provided for the reception of a, screw e'elongated at its inner end to form a pin passing through a central hole of the diaphragm and adapted to abut against the centre of the opposite .capaoity surface a, so that when the "screw' e is screwed down towards and against the capacity surface a, the same will cause the latter to bulgeand form spherical cavities or calottes in opposition.- It will be seen that thus the cross-sectional width of the gap in which the diaphragm is free to oscillate, is greatest at the centre of the diaphragm and decreases gradually towards the periphery of the latter. The dia hragm is caused to oscillate when excited hy electrical alternating voltages, as described in. de tailin the prior application Serial No. 306; 158 herein referred to.

In the centre of the concave surface of the capacity body a there is provided a small I disk d of lnsulating material'for the purpose of preventing the pressure difference-v of the two surfaces a and a from being bal- Y the heads 9' and g of the draw-screws f and A f, respectively, are embeddedin bushings or sockets It and h, respectively-,supported. by or integral with bridles i and i, respec-i tiveliytwhereof the extremities engage and are rmly connected with the rims l0 and k of the capacity bodies a and 0;, respectively.

Th threaded endsgigof the screw shafts engage in correspondingly threaded bores. the alined axes of which coincide with the centre of the diaphragm, so that on turning the screws f and f in one direction the two opposite centres of the capacity surfaces a and a will recede from the diaphragm and the capacity surfaces will thus be given thedesired concavity.

In the modification shown in Figure 4 the heads'or outer ends of'the screws 4 and f are supported by the protective gri s m and m, respectively, usually provided for the purpose of protecting the" condenser from external disturbing influences so thatthe heads .of the screws abut against the said grids-when the screws are turned in order to give the capacity surface the desired shallow. concavity.-. I I have hereindescribed and shown several practical constructions" .ofmypresent improvements, butit will beapparent that the device, articularly the adnisting means, is

suscepti 1e of embodiment 1n various other alternative forinm w thout departure from the invention whereof the chief features resides in the shallow. bulged form or concavity of the two capacity surfaces'or in the means provided for imparting to the latter a shallow bulged form or concavity whereofthe' radius of curvature is adjustable for th purpose of positioning the said two suraces as'close by the vibratile diaphragm as can be done without interfering with the oscillatory movements of the latter. Itherefore, reserve the privilege of resorting to all such legitimate changes as may be fairly embodied within the spirit and scope of the invention as claimed.

What I claim is 1. A sounding condenser comprising two firmly interconnected capacity. surfaces, a

vibratile diaphragm disposed midway be? tween the said two surfaces, and means for causing the said capacity surfaces to bulge inopp osed directions with relation to each other soas to form shallow concavities with the diaphragm freely sandwiched therebetween. v

2. A sounding condenser comprising two y-interconnected capacity surfaces, a vibratile'diaphragm disposed midway between the said two surfaces, a screw engaging withits threaded end in a threaded cen- I tral bore of the one capacity surface, and abutting with its otherend against the other capacit surface, and meansfor insulating thesai screw with relation to'the said other capacity surface, substantially as and for the purpose set forth.

In testimony whereof I aflix my signature.

' HANS VOGT. 

